Power MOSgated devices such as power MOSFETs and IGBTs are well known. Such devices may employ a planar or tench type active area but a termination structure is needed to terminate the active area. Such termination structures frequently employ spaced field rings and field plates. These require considerable area of the silicon die, particularly for high voltage devices, and increase the necessary die area. Generally, the termination size is about 3 to 5 times the required junction-receiving epitaxial silicon layer thickness, which increases as a function of blocking voltage capability. Thus, a planar termination requires space to “ramp down” the electric field from the edge of the active area to the device edge. The higher the device voltage is, the larger is the proportion of termination area to die area.
It would be very desirable to reduce the termination area without impacting the reliability of the termination.